The appropriate treatment regimen for dehydration mandates the accurate assessment of fluid deficit and the gradual correction of that deficit. To this end, the skin turgor test (a.k.a. the skin pinch test) is widely performed to assess the degree of fluid loss or dehydration. This highly subjective test has been found, in numerous studies, to be an inaccurate measure of dehydration in all but the most severe cases and hence is not suitable for assessing overall hydration status. Alternatively, new techniques able to measure the galvanic skin response (GSR) have resulted in the demonstration of wearable devices able to quantify the relative hydration level of the wearer. However, it is widely realized that this, too, is a highly inaccurate measure of hydration as the measurement is easily confounded by the sympathetic nervous system response, amount of adipose tissue, temperature, humidity, and hydration of the stratum corneum itself, which can be skewed by age as well as various topical creams and ointments. This project aims to address the above limitations of conventional hydration monitoring techniques via the development of a non-invasive hydration-sensing patch. The proposed device leverages our team's latest innovations in electrochemistry, screen printing, conducting polymers, and surface functionalization to tender the real-time profile of circulating sodium levels in a non-invasive, pain-free fashion, thereby leading to substantially improved clinical outcomes among the elderly population. Expected outcomes from this research project include: (1) the development of epidermal adhesive biosensors containing a sodium ion-selective layer and (2) the ability to fabricate the said sodium biosensors employing high-throughput, low-cost screen-printing methods. This agglomerates innovative techniques for the functionalization of the printed electrode contingent and relies on the development of ion-selective membranes in connection with novel methods of electrochemical transduction. The salient features of this epidermal biosensor platform include high sensitivity, stability, selectivity, simplicity, versatility, and robustness at a price that i amenable to widespread healthcare adoption. This paradigm enables the individual to take proactive measures to assess their hydration throughout their daily routine, thereby mitigating the likelihood of hospital admission due to hypernatremic dehydration. In addition to tendering real-time feedback to the wearer, this unique approach can leverage the wireless infrastructure to relay the data to the healthcare provider for review, trending, and archiving.